1. Field of the Invention
The present invention relates to the field of shoe-making, and more particularly to the method of manufacturing shoes, wherein a shoe assembled integrally with all parts thereof bonded and joined on a last is conveyed to a rapid-freezing apparatus in which the shoe is cooled rapidly by means of liquefied gas so as to obtain a shoe fitted exactly to the last and to manufacture the shoe, the commercial value being enhanced, in a short time and highly efficiently in a semiautomated or an entirely automated shoe-manufacturing process.
2. Prior Art
As for a prior shoe manufacturing method, a direct-binding manufacturing method (cemented manufacturing method) is known in the art. Although the parts differ a little according to the kinds of shoes, the manufacturing method for the standard type of shoes will be explained as a typical example. In the prior manufacturing method, first of all the uppers which are assembled from the toe-caps, the right and left sides and the boxings (back parts of the shoes) cut out according to their respective proper configurations and the insoles are pressed onto the shoe lasts. At the same time, those uppers and soles are lasted each other exactly on the peripheries of the lasts by means of tacking and/or gluing their overlapped edges and then are joined integrally by means of heat-setting. After that, the bottoms of the shoes are secured to the undersides of said lasted soles by means of gluing and pressing and then the heels thereof are secured to the bottoms accordingly. At the final finishing step, the enamel or the varnish for shoes is sprayed onto the outside surfaces of said joined shoes by means of spray gun.
On the other hand, even though the commodity value for the shoes is estimated from general point of view, actually it greatly depends on the finishing condition of the shoe surfaces and shapes. Accordingly, the following conditions are essential for the enhancement of the commodity value for the shoes. That is, (1) the shoes surfaces should be smooth. (2) And the uppers should be gotten into "habits" so as to retain the shapes in accordance with the lasts. That is, (2-a) the top-lines of the shoes should be formed proportionally so as to keep them in shape. (2-b) And the shapes of the shoes should be kept correctly without being shrunk or wrinkled, especially so as to properly maintain the correct shaped contours of the toe-caps.
However, in said prior manufacturing method, the temperature of the shoe surfaces rises to 65.degree..about.70.degree. C. for the heat-setting, and said surfaces are still kept at such hot temperature as 25.degree..about.35.degree. C. at the end of the bottom press-securing step. Hence, in the case where the lasts are removed from the shoes just after the bottom securing, the commodity value thereof is apt to be diminished greatly because the shoes get out of shape until shipping.
Therefore, in order to prevent such a disfigurement as above-mentioned, as shown in U.S. Pat. No. 4,304,020 and U.S. Pat. No. 4,528,710, it is necessary to have such a finish step because the shoes are allowed to stand for a certain time and cool down naturally at room temperature or to be cooled gradually by supplying cold air thereto between said bottom securing step and the last removal step and then the shoes from which the lasts are removed are also allowed to stand undisturbed in storage.
However, in the known method as shown in said prior art, it needs a long time for the shoes to cool down because the finish step is carried out with a slow way of cooling down, and during that time a physical change is apt to take place in a certain quality of leather so as to cause a disfigurement in a portion of the shoes which may diminish the commodity value and must be corrected later.
Further, as shown in the above-mentioned prior art, in a general shoe manufacturing method there is provided a conveyer line which covers a through process from the assembly step to the finish step. For example, in said cemented method, since the rate taken by the line for the steps following the finish step relative to the entire manufacturing line is comparatively large and the cooling time is protracted due to the slow cooling down, disadvantageously the manufacturing efficiency is lowered according to the protracted time and the entire manufacturing line is scaled up according to the extended line for the steps following the finish step.
Furthermore, since more lasts are needed in proportion to the extended manufacturing time and line, the turnover rate of the last utilization is lowered accordingly. Owing to the delay of the finishing work which might influence the stabilizing time succeedingly and the stabilizing time which must be long enough to make the shoe shape stabilized, it takes too many days from manufacturing to shipping.